This invention relates to highly branched synthetic hydrocarbon fluids (SHF) produced by non-destructively hydrogenating anionically oligomerized dienes or polydienes, having utility as traction fluids and to a method of operating traction drives using the described synthetic hydrocarbon fluids.
High traction fluids give superior performance in traction drives. A traction drive transfers force from one rotating shaft to another through a rolling contact. The transfer is efficient if there is "minimal" slippage. This is a function of the traction coefficient which is defined as the force transmitted divided by the normal force which keeps the rolling members in contact or as being the quotient of the traction due to the transmission of the traction between the driving and driven elements and the normal force (normal load) between the driving and driven elements. Slip may be defined as being the absolute value of the quotient of the difference between the two circumferential speeds of the roller elements and the greater circumferential speed. The maximum coefficient of traction is preferably as high as possible in order to achieve maximum power transmission per unit load.
Various fluids have been proposed and/or utilized as traction fluids. For example, U.S. Pat. No. 3,411,369 discloses fluids comprising fused, saturated carbon containing rings; U.S. Pat. No. 3,440,894 discloses fluids comprising organic compounds containing a saturated carbon containing ring or an acyclic structure having at least three quaternary carbon atoms; U.S. Pat. No. 4,499,000 discloses power-transmission fluids containing cyclic ketals derived from alicyclic ketones. Generally speaking, the prior art generally used mineral oils as the lubricant basestock or were limited to synthetic fluids having low viscosity grades.
It has now been discovered that synthetic hydrocarbon fluids with high traction coefficients throughout a wide range of viscosity grades are obtainable from the hydrogenation of highly branched (large amounts of 3,4-enchainment) isoprene oligomers. These fluids have traction coefficients equivalent to or higher than traction fluids currently commercially marketed. Additionally, they show better performance in terms of lubricant protection in elastohydrodynamic lubrication (EHL)--the mode of lubricating in which traction drives operate. These hydrogenated polyisoprene (HPI) fluids can be produced in any viscosity grade. The highly branched synthetic hydrocarbon fluids of the present invention, to the best of applicant's knowledge, have not previously been used as fluids for traction drive applications.